In double twist twisting frames, the threads to be twisted must be threaded from the stationary supply bobbin, through the hollow spindle to the storage disc and in the latter they must be threaded radially outwardly. For this purpose a threading device of the type mentioned initially is known (from German Auslegeschrift 1,289,470) in which the suction device consists of a shaped member which can be applied to the storage disc and in which an injector nozzle is arranged. By means of this injector nozzle there is created at the opening of the storage disc a vacuum which is effective through the hollow spindle as far as the upper opening thereof. If thread breakage occurs between the supply bobbin and the storage disc, or if a thread has to be freshly threaded through the hollow spindle, in the first place the shaped member must be moved upwards of the storage disc. This can be effected by providing in the region of each spindle a shaped member which is pivotal about a horizontal axis, or by constructing the shaped member as a hand instrument which is carried by an attendant from spindle to spindle. After the shaped member has been applied to the storage disc, the compressed air is turned on so that the vacuum referred to is created at the upper end of the spindle. At this instant the attendant must hold the end of the thread to be threaded at the upper opening so that the end of the thread is sucked into the spindle. Previously or simultaneously, however, the attendant must draw a suitably long length of thread from the supply bobbin and hold it in order that this length of thread may be sucked into the hollow spindle with the least possible resistance. The suction effect at the upper end of the hollow spindle is relatively small owing to the flow losses occurring through the long and narrow hollow spindle. It is however particularly disadvantageous that the attendant has to remain at the spindle for a long time, during the whole of the threading operation. Also, the said suction devices have to be provided at each spindle if one attendant is not to have to carry a hand instrument from spindle to spindle, which is likewise laborious and time consuming.
Threading devices driven by compressed air are also known (from French Pat. No. 1,045,449) which also have to be carried about by an attendant. These have a blower nozzle and a mouthpiece adjoining the nozzle. The mouthpiece, which can be placed on the upper end of the hollow spindle, has a slot at its rim facing the spindle. The thread is sucked into this slot by the injector effect of the blower nozzle and is then conveyed through the spindle by the current of blowing air. In this case also the attendant must remain at the spindle during the whole of the threading operation and draw the piece of thread to be threaded from the supply bobbin, apply it to the mouthpiece and guide it during the threading operation.
The invention is based on the problem of providing a threading device of the type mentioned initially which to a great extent automatically performs the actual threading of the thread, is simple in construction and with which an attendant does not have to be present either at the beginning of the threading operation or during the threading operation at the particular twisting point. In accordance with the invention this is achieved in that there is provided, on a service carriage which is known in itself and is movable along at least one side of a frame, a threading head driven by compressed air which is movable from a rest position in which it is spaced from the spindle into a threading position in which it registers with the upper end of the spindle or with the opening of a thread brake arranged there, the threading head having, at the end facing the spindle axis, a threading slot that extends parallel to the spindle axis, which slot reaches as far as a thread channel provided in the threading head and registering in threading position with the spindle axis, and in that there are arranged on the frame in the region of each spindle at least two holder elements spaced one above the other and substantially in the plane of movement of the threading slot, between which elements the thread to be threaded can be hung and hence can be presented to the threading head.
By means of this novel threading device largely automatic threading of the thread through the spindle and storage disc is possible without an attendant having to be present at the beginning of the threading operation or during this operation. If the attendant notices a breakage of thread between the supply bobbin and the storage disc, or if the thread is to be threaded anew into a spindle, he has only to draw a length of thread from the supply bobbin and hang this length of thread on the two holder elements. He can then immediately proceed to the next spindle to be serviced or perform other work. The attendant does not need to present the end of the thread to the upper end of the hollow spindle and also he does not need to guide the thread until it is threaded through the hollow spindle and the storage disc. To this extent the attendant's work is reduced to a minimum and indeed to manual operations that are very easy to perform. The presented thread is, at a suitable time, when the service carriage has reached the spindle concerned and has come to a standstill, engaged by the threading head provided on the service carriage and brought over the upper end of the spindle, the suction device being simultaneously moved into the vicinity of the storage disc. Thereupon the thread to be threaded can be threaded through the spindle and the storage disc under the blowing action of the threading head and the suction of the suction device. Since the suction device and the threading head are carried along with the service carriage, only one of these devices needs to be provided, viz. not one for each spindle. Moreover, since the service carriage carries other assemblies for the performance of other work such for example as threading and conveying away the end of the thread hanging from the storage disc, or knotting, the threading device according to the invention does not involve any additional expenditure on manufacture or servicing as regards the service carriage. It is further of advantage to provide a shears that can be inserted into the region between the two holder elements and in the vicinity of the lower holder element. The distance of the shears from the upper holder element is such that the end of the thread to be threaded is located closely over the upper end of the spindle when the threading head has moved into its operative position and has engaged the thread to be threaded. The shears also ensures that the threading head always receives a predetermined length of thread independently of what length of thread was actually drawn from the supply bobbin by the attendant and presented.
Most double twist twisting frames have thread brakes arranged in the hollow spindle, the braking members (balls or the like) can be brought away from the coacting brake rings for the purpose of threading. This cutting out of the thread brakes is generally effected by exerting an axial, downwardly directed pressure on the upper end of the spindle. A further form of the invention will also permit the threading of a spindle equipped with such thread brakes without an attendant. This is achieved by providing on the threading head a downwardly movable slide which in the operative position of the threading head coacts with the thread brake provided on the spindle. When the threading head has reached its operative position, this slide is moved downwardly and presses on the upper end of the spindle or of a thread brake located on the spindle. In this way the thread brake is cut out and a passage for threading is freed through the thread brake. In the case of thread brakes that are cut out by pulling a part of the thread brake upwards, the slide must be so constructed that it engages and lifts this part to be lifted upwardly.